drm/i915: Switch back to an array of logical per-engine HW contexts

We switched to a tree of per-engine HW context to accommodate the
introduction of virtual engines. However, we plan to also support
multiple instances of the same engine within the GEM context, defeating
our use of the engine as a key to looking up the HW context. Just
allocate a logical per-engine instance and always use an index into the
ctx->engines[]. Later on, this ctx->engines[] may be replaced by a user
specified map.

v2: Add for_each_gem_engine() helper to iterator within the engines lock
v3: intel_context_create_request() helper
v4: s/unsigned long/unsigned int/ 4 billion engines is quite enough.
v5: Push iterator locking to caller

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190426163336.15906-7-chris@chris-wilson.co.uk

1 files changed, 37 insertions, 33 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 166a33c0d3ed..679f7c1561ba 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2076,9 +2076,7 @@ gen8_dispatch_bsd_engine(struct drm_i915_private *dev_priv,
 	return file_priv->bsd_engine;
 }
 
-#define I915_USER_RINGS (4)
-
-static const enum intel_engine_id user_ring_map[I915_USER_RINGS + 1] = {
+static const enum intel_engine_id user_ring_map[] = {
 	[I915_EXEC_DEFAULT]	= RCS0,
 	[I915_EXEC_RENDER]	= RCS0,
 	[I915_EXEC_BLT]		= BCS0,
@@ -2086,10 +2084,8 @@ static const enum intel_engine_id user_ring_map[I915_USER_RINGS + 1] = {
 	[I915_EXEC_VEBOX]	= VECS0
 };
 
-static int eb_pin_context(struct i915_execbuffer *eb,
-			  struct intel_engine_cs *engine)
+static int eb_pin_context(struct i915_execbuffer *eb, struct intel_context *ce)
 {
-	struct intel_context *ce;
 	int err;
 
 	/*
@@ -2100,21 +2096,16 @@ static int eb_pin_context(struct i915_execbuffer *eb,
 	if (err)
 		return err;
 
-	ce = intel_context_instance(eb->gem_context, engine);
-	if (IS_ERR(ce))
-		return PTR_ERR(ce);
-
 	/*
 	 * Pinning the contexts may generate requests in order to acquire
 	 * GGTT space, so do this first before we reserve a seqno for
 	 * ourselves.
 	 */
 	err = intel_context_pin(ce);
-	intel_context_put(ce);
 	if (err)
 		return err;
 
-	eb->engine = engine;
+	eb->engine = ce->engine;
 	eb->context = ce;
 	return 0;
 }
@@ -2124,25 +2115,19 @@ static void eb_unpin_context(struct i915_execbuffer *eb)
 	intel_context_unpin(eb->context);
 }
 
-static int
-eb_select_engine(struct i915_execbuffer *eb,
-		 struct drm_file *file,
-		 struct drm_i915_gem_execbuffer2 *args)
+static unsigned int
+eb_select_legacy_ring(struct i915_execbuffer *eb,
+		      struct drm_file *file,
+		      struct drm_i915_gem_execbuffer2 *args)
 {
 	struct drm_i915_private *i915 = eb->i915;
 	unsigned int user_ring_id = args->flags & I915_EXEC_RING_MASK;
-	struct intel_engine_cs *engine;
-
-	if (user_ring_id > I915_USER_RINGS) {
-		DRM_DEBUG("execbuf with unknown ring: %u\n", user_ring_id);
-		return -EINVAL;
-	}
 
-	if ((user_ring_id != I915_EXEC_BSD) &&
-	    ((args->flags & I915_EXEC_BSD_MASK) != 0)) {
+	if (user_ring_id != I915_EXEC_BSD &&
+	    (args->flags & I915_EXEC_BSD_MASK)) {
 		DRM_DEBUG("execbuf with non bsd ring but with invalid "
 			  "bsd dispatch flags: %d\n", (int)(args->flags));
-		return -EINVAL;
+		return -1;
 	}
 
 	if (user_ring_id == I915_EXEC_BSD && HAS_ENGINE(i915, VCS1)) {
@@ -2157,20 +2142,39 @@ eb_select_engine(struct i915_execbuffer *eb,
 		} else {
 			DRM_DEBUG("execbuf with unknown bsd ring: %u\n",
 				  bsd_idx);
-			return -EINVAL;
+			return -1;
 		}
 
-		engine = i915->engine[_VCS(bsd_idx)];
-	} else {
-		engine = i915->engine[user_ring_map[user_ring_id]];
+		return _VCS(bsd_idx);
 	}
 
-	if (!engine) {
-		DRM_DEBUG("execbuf with invalid ring: %u\n", user_ring_id);
-		return -EINVAL;
+	if (user_ring_id >= ARRAY_SIZE(user_ring_map)) {
+		DRM_DEBUG("execbuf with unknown ring: %u\n", user_ring_id);
+		return -1;
 	}
 
-	return eb_pin_context(eb, engine);
+	return user_ring_map[user_ring_id];
+}
+
+static int
+eb_select_engine(struct i915_execbuffer *eb,
+		 struct drm_file *file,
+		 struct drm_i915_gem_execbuffer2 *args)
+{
+	struct intel_context *ce;
+	unsigned int idx;
+	int err;
+
+	idx = eb_select_legacy_ring(eb, file, args);
+
+	ce = i915_gem_context_get_engine(eb->gem_context, idx);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
+
+	err = eb_pin_context(eb, ce);
+	intel_context_put(ce);
+
+	return err;
 }
 
 static void